You can actually have an FPU with the TF1230

68030 + SDRAM + IDE

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alenppc
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You can actually have an FPU with the TF1230

Post by alenppc »

I decided to solder an FPU on the motherboard of my ReAmiga 1200 to see what would happen:
fpu1.jpg
fpu1.jpg (530.65 KiB) Viewed 4535 times

Much to my surprise, it turns out the FPU remains active with the TF1230 plugged in and works normally.
fpu2.jpg
fpu2.jpg (414.1 KiB) Viewed 4535 times

Even though it only runs at 14 mhz, It gives you a 57% boost in FPU operations over the TF1230 alone.
fpu3.jpg
fpu3.jpg (145.28 KiB) Viewed 4535 times

And the addition of the onboard FPU does NOT break the TF1260 compatibility, but before anyone asks, no, you cannot use an external FPU with an 060 processor, it simply won't be visible once the TF1260 is plugged in.
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supaduper
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Re: You can actually have an FPU with the TF1230

Post by supaduper »

Just add to Alens post, yes you can just slap an 882 FPU on the A1200, mine is a 1D4 and it will work with the TF1230 but obviously only at the 14mhz as Alen states , but hey you can have a FPU with a TF1230, and just take note not all accelerators are friendly with an added FPU so if you really wanted to do it I would use a 68 pin socket, but be carefeful those pads are flakey and do not like a lot of heat :)
alenppc
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Re: You can actually have an FPU with the TF1230

Post by alenppc »

Actually, I tried a bunch of accelerators and it does not cause issues with any of them.

These are my test results:

TF1230: works fine with the motherboard FPU
TF1260: ignores the motherboard FPU (not visible)
ACA1231: ignores the motherboard FPU (not visible)
ACA1232: ignores the motherboard FPU (not visible)
M-Tec 1230/42 MHz with onboard FPU: uses the onboard FPU and ignores the motherboard one.

So it's a pretty safe thing to do. The only potential problem might be simple ram expansions with onboard FPU, but I am not sure as I don't have any to test.

Also it should be very easy and trivial to clock the motherboard FPU at 28 MHz with a jumper wire (although I haven't tried yet).
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Re: You can actually have an FPU with the TF1230

Post by Aeberbach »

So my TF1230 isn't completely useless after all! Yay! :lol:
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supaduper
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Re: You can actually have an FPU with the TF1230

Post by supaduper »

Adding to Alens FPU compatiblity list:

Blizzard 1260 works fine and uses the 060 50mhz FPU
Blizzard 1220/4 (+4mb too) works fine and sees the A1200 onboard FPU

To be honest this is great and if we can do a simple hack as Alen suggest we can double it up to 28mhz:)
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Re: You can actually have an FPU with the TF1230

Post by Danoo »

Thanks for this info, will add a socket to one of my 1200 MBs and check it out :)
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screemo
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Re: You can actually have an FPU with the TF1230

Post by screemo »

But why not add a plcc to pga adapter, add a mc68882rc50a clock it to 56mhz ? :D

I'm rambling here I know ......
alenppc
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Re: You can actually have an FPU with the TF1230

Post by alenppc »

screemo wrote: Fri Jan 28, 2022 1:16 pm But why not add a plcc to pga adapter, add a mc68882rc50a clock it to 56mhz ? :D

I'm rambling here I know ......
To be honest I don't think the motherboard will fit back in the case even if you add a socket, although I am curious to know if the 882 can run in a completely asynchronous manner from the motherboard, in which case you could even add a small oscillator to clock it at will. I will experiment when I get some time.
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Badwolf
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Re: You can actually have an FPU with the TF1230

Post by Badwolf »

alenppc wrote: Fri Jan 28, 2022 1:37 pm To be honest I don't think the motherboard will fit back in the case even if you add a socket, although I am curious to know if the 882 can run in a completely asynchronous manner from the motherboard, in which case you could even add a small oscillator to clock it at will. I will experiment when I get some time.
The 68882 is designed to run asynchronously but it depends how nicely the rest of the system plays with it. From my experience playing with my Falcon board, the FPU will run happily at a speed greater or equal to that of the CPU, but only down to about CPUCLK/2.

My current board has the CPU at 50MHz and the FPU at 25.

Also be aware, at least for the PLCC 68882, they will work work at faster speeds on some operations than others. Test all operations properly and clock slower if if any doubt. I have four chips here all labelled 40MHz. One passes all the tests at 40, two at 25 and one only at 16. Yet they will all be recognised and pass *some* tests at 50.

Here be dragons.

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Re: You can actually have an FPU with the TF1230

Post by markus0321 »

alenppc wrote: Wed Jan 26, 2022 4:12 pm Actually, I tried a bunch of accelerators and it does not cause issues with any of them.

These are my test results:

TF1230: works fine with the motherboard FPU
TF1260: ignores the motherboard FPU (not visible)
ACA1231: ignores the motherboard FPU (not visible)
ACA1232: ignores the motherboard FPU (not visible)
M-Tec 1230/42 MHz with onboard FPU: uses the onboard FPU and ignores the motherboard one.

So it's a pretty safe thing to do. The only potential problem might be simple ram expansions with onboard FPU, but I am not sure as I don't have any to test.

Also it should be very easy and trivial to clock the motherboard FPU at 28 MHz with a jumper wire (although I haven't tried yet).
I have a revision of the A1200 2B board and I do not see a jumper for 28MHz FPU on it, I also do not see such a possibility in the diagram. I soldered the FPU socket and it works fine for me, but where can I find this 28MHz jumper for FPU on the board?
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